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Practitioners need to consider different approach for parasite control in kittens

Adult female earmite, Otodectes cynotisaption, can be directly acquired by kittens from their mother.

Parasite control in kittens requires knowledge of the pathogens involved and the capabilities of the different products for controlling the parasites of interest. This article will review the parasites and their mode of transmission to kittens. It will then examine the various products available for parasite control in kittens. Also, it will look at kittens as potential sources of agents of zoonotic importance. Finally, it will examine various means of ensuring that kittens are protected from these infections.

Fleas can cause severe anemia and death in kittens, so it is essential that they be protected from these parasites.

Internal parasites
Kittens acquire only a few internal parasites from the queen directly. The only common internal parasite that is acquired from the queen after birth is the common feline roundworm Toxocara cati, which is transmitted to the kittens in the milk. It is unclear when the kittens will first shed eggs in their feces after transmammary infection, but it seems that the first eggs would be shed no earlier than one month after birth. Kittens can acquire congenital toxoplasmosis from the queen, but it appears that this is most likely if the queen is infected for the first time while pregnant. Congenitally infected kittens appear to develop disease but do not appear to shed any significant number of oocysts. The relatively rare intestinal fluke, Alaria marcianae, can infect kittens via the milk of the queen, but these infections are seldom life threatening, and eggs in cat feces pose little risk to owners because an intermediate host is required in the life cycle of this parasite. There is neither transmammary nor transplacental infection of kittens with the feline hookworms, Ancylostoma tubaeforme and Ancylostoma braziliense; thus, hookworms do not pose the same risk to kittens that Ancylostoma caninum poses to puppies.

Table 1: Antiparasitic products for cats and their label claims

Ectoparasites
There are a number of ectoparasites that kittens can acquire by direct contact with the queen as she cares for them. These include: fleas (Ctenocephalides felis), lice (Felicola subrostratus), ear mites (Otodectes cynotis), mange mites (Notoedres cati), and the fur mites (Cheyletiella blakei and Lynxacarus radovskyi). Thus, kittens, when nursing, are at risk on becoming infested with some of the insect and arachnid pathogens that are present on the queen. Only two of these pathogens are common in cats, fleas and ear mites, so the risk of kittens acquiring infections with these other pathogens is rather rare. Also, with the exception of fleas, these pathogens are typically not life threatening to kittens. Fleas on the other hand, can cause severe anemia and death in kittens, so it is essential that they be protected from these parasites. It is also believed that flea feces are the source by which cats are infected with the cat-scratch fever agent, Bartonella henselae; thus, this is another reason to keep cats free of fleas.

Direct transfer to kittens via feces can occur with respect to a few parasitic pathogens. Queens shedding Giardia felis or Cryptosporidium felis in their stools can directly infect young nursing kittens. In a similar fashion, they can infect kittens with intestinal trichomonads. The only helminth that would be directly infectious to kittens is the stomach worm Ollulanus tricuspis, which is transmitted in feces or vomitus; but fortunately, Ollulanus tricuspis is only relatively rare in cats.

Table 2: Age of first administration of antiparasiticides labeled for cats

Other risk factors
There are a number of fecal stages passed by queens that are capable of developing in the environment rather rapidly and infecting kittens soon after birth. The most common of these pathogens would be the coccidians, Isospora felis and Isospora rivolta, which can cause disease in neonatal kittens. Infective stages of these parasites could appear in the feces of cats as soon as a week after birth. Also, the other roundworm that infects cats, Toxascaris leonina, has an egg that rapidly develops to the infective stage, and it can often infect cats while they are still quite young, although it will take about two months before eggs would appear in the feces of the kittens. If hookworm eggs are shed by the queen into a warm moist soil environment around the kitten, infective-stage larvae could develop and be a source of neonatal infection in kittens. Kittens could contaminate the environment with hookworm eggs as soon as two weeks after birth, but more likely not until they were about 4 to 6 weeks old. (They would need to move about in the contaminated soil to get infected, and it would take two weeks for the worms to mature.)

Eggs of Toxocara cati. Kittens need to be protected against roundworms and other parasites to avoid serious medical problems.

There are two parasites that can be important in kittens and which infect cats through arthropod vectors. The flea tapeworm, Dipylidium caninum, infects kittens if they ingest infected fleas. The kittens can shed segments within three weeks of having eaten the flea, and it is possible that large numbers of these tapeworms could cause impaction of the small intestine. Kittens also can be infected with heartworms by mosquito bites, but it is unclear how often this is an important disease in very young animals.

Treatment and control
The products that control parasites in cats only are effective against a very few of the parasites previously listed. Infections with giardiasis, coccidiosis, cryptosporidiosis and toxoplasmosis will be treated using various off-label combinations of products or through the use of various palliatives for the signs of infection. Similarly, the rare nematode or trematode infection will be treated only when diagnosed. Control programs have to be targeted at the common parasites. Thus, the available products labeled for parasite control in cats treat or control infections with roundworms, hookworms, heartworm, tapeworms, fleas and ear mites (Table 1, p. 14). Frontline® Plus provides broad-spectrum protection against ticks and protects against adult fleas and also has effects against the developing larval stages of fleas. Advantage™ protects cats against adult fleas. These products differ as to the time they can be first administered to kittens (Table 2), and it should be noted that one of the most common products for treating hookworms and roundworms in kittens, pyrantel pamoate, does not appear on the list of labeled products for cats. Thus, the standard of treating kittens with Nemex or Strongid T (at 20 mg pyrantel pamoate per Kg of body weight), is an off-label use of both products.